Abstract Background Maintaining the integrity of the structure and function of piglet intestines is crucial for their growth and health. This study aims to evaluate the effects of an antibiotic free diet supplemented with bile acid on gut health and growth performance of weaned piglets, and to explore their regulatory mechanisms. Methods Thirty-two weaned piglets were randomly divided into two groups and fed either a basal diet or a basal diet supplemented with 350 mg/kg bile acid. Results Dietary supplementation with bile acid increased the average daily gain (ADG) and final weight of piglets, and reduced the diarrhea incidence (P